public class Solution {
    public String modifyString(String ss) {
        char[] s = ss.toCharArray();
        int n = s.length;
        for(int i = 0;i < n;i++) {
            if(s[i] == '?') {
                for(char ch = 'a';ch <= 'z';ch++) {
                    if((i == 0 ||ch != s[i-1]) && (i == n-1 || ch != s[i+1])){
                        s[i] = ch;
                        break;
                    }
                }
            }
        }
        return String.valueOf(s);
    }

    public static void main(String[] args) {
        Solution solution = new Solution();
        String ss = "ubv?w";
        System.out.println(solution.modifyString(ss));
    }
}
